The colorful packages on store shelves are adorned with the images of cartoon characters and are marketed as incense or potpourri. But some children are smoking the contents as a substitute for marijuana, and Middleborough Selectman Allin Frawley says the results can be deadly.

Frawley is calling emphatically for the town to impose a bylaw banning these products, and selectmen will hold a public hearing on Monday to discuss the proposed ordinance.

“I personally feel that this is a health emergency in this town,’’ Frawley said at last week’s selectmen’s meeting, where he cited federal data that show effects ranging from total kidney failure to psychosis.

Synthetic cannabinoids, as they are known, are sold in smoke shops, convenience stores, and gas stations. They are designer drugs created by spraying chemicals on herbs. When smoked, the drug simulates the effects of THC, the chief ingredient in marijuana, according to the federal Centers for Disease Control.

Although labels on the products can say “Not for Human Consumption,” the warnings are often ignored and the “incense” has become a popular alternative to marijuana, appealing to teens and young adults, officials said.

Several bills to ban the products in Massachusetts have languished on Beacon Hill over the past few years.

Congress and more than 45 states and Puerto Rico have blocked the sale of a host of these substances, which have been sold under such names as Spice and K2. The laws generally ban specific substances or classes of substances, but according to the National Conference of State Legislatures, new versions continually enter the market as manufacturers make minor changes to the chemical composition, creating new, but very similar, drugs that aren’t covered in the law.

Taunton is the only Massachusetts community that has taken action on what Frawley has proposed. The city’s mayor signed a law on Aug. 1 that imposes a $150 fine for a first offense, and $350 after that, for those caught selling, possessing, or using the products.

In Middleborough, the challenge will be to write a bylaw that closes the loophole on new formulations. Town health officer Jeanne Spalding said she has worked up a draft proposal at to Frawley’s request, but it still needs a lawyer’s review.

School Superintendent Roseli Weiss, who attended the selectmen’s meeting last week, said the district’s middle-school and high-school principals are aware of the products in question, but have thankfully had no run-ins with them.

School officials will support town measures to keep children safe, she said.

One of the currently available products comes in a psychedelic package bearing the words “Scooby Snax potpourri” and the image of a cross-eyed Scooby-Doo, the dog from a popular children’s cartoon.

During last week’s meeting, Frawley held up a picture of Scooby Snax and said he will withhold his business from any local store that sells the products, and urged all town residents to do the same.

“My 3-year-old watches Scooby-Doo, and doesn’t understand that this is poison,’’ he said. “What the stores are doing is not illegal, but that doesn’t make it right.”

After hearing of Frawley’s plan, state Representative Thomas Calter, a Kingston Democrat, pledged to file legislation on behalf of the town, which is partly in his district.

Frawley said he appreciates the effort. But rather than waiting for a state law to pass, Middleborough should enact its own bylaw through the town’s Health Department, he said.

Once the bylaw is enacted, the research and framework used to prepare the ordinance can be shared with surrounding towns, he said, which would bring about action that is broader and faster.

Middleborough Selectwoman Leilani Dalpe said her research shows the products are also linked to violent behavior and heart failure.

“The faster we get them out of town the better,’’ she said.

Jeff Jacobson, director of training and education for Brewster Ambulance Service, said in an e-mail that he reviewed 25 of 75 cases from Middleborough last year where the patient showed overdose symptoms. Of those, he said, four were thought to be a direct result of synthetic marijuana.

Jeff Lenard, a spokesman for the National Convenience Store Association, said some store owners may be unwittingly selling harmful products that they believe are being used for benign purposes.

“But, if they act like a head shop, then they are a head shop, and we can’t condone that,’’ Lenard said.

He urged selectmen and anyone with questions about what products a store sells to speak openly with the owner and start a conversation, rather than a fight.

“I would suspect there are a fair amount who would have no idea about this product, and stock it,’’ he said.

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